The present invention relates to an object-coating spray gun defined in the preamble of claim 1.
In particular the invention relates to a spray gun coating objects with a powder coating material. However the invention is not restricted to this specific implementation and also may be used to coat objects with liquid coating materials.
A object-coating spray gun of this kind is known from the European patent document 0 383 030 A. Therein the gun structure consists of a barrel and of a separate grip affixed to it. A powder tube configured at an angle corresponding to that subtended between barrel and grip is inserted first into this grip and then from the rear into the barrel, the grip and barrel being connected in the process. The powder tube may be integral or consist of two tube segments mutually joined at their crossing site before being inserted into grip and barrel. A chamber to receive a high-voltage generator is configured in the barrel above the powder duct and runs as far as above the grip zone. At least one high-voltage electrode to electrostatically charge the coating powder is connected to the high-voltage generator at the downstream barrel end.
U.S. Pat. No. 3,777,981 discloses a spray gun which coats objects with coating powders and comprises a barrel-affixed grip and a flexible powder hose running through grip and barrel. Moreover spray guns are known from the German Auslegeschrift 20 30 388 and from the German patent document 3545885 C for coating objects with liquid coating powder and fitted with a grip affixed to a barrel.
Powder spray guns generate a fine dust undesirably penetrating the gun or forced out of the gun at interfaces which per se are sealed hermetically. As regards liquid-coating spray guns, there is the danger that atomized liquid particles shall deposit at interfaces of the spray gun. Both spray guns coating by means of powder and by means of liquids run the danger that high-voltage leakage paths shall be created at the interfaces between the high-voltage components electrostatically charging the coating material and the gun segments which must be electrically insulated therefrom.
The objective of the invention is to so design the spray gun that no leakage shall arise. The spray gun of the invention is of simple and economical design and requires practically no maintenance work.
In accordance with an aspect of the present invention, the second line segment is fitted with an extension which is impermeable to the coating material and which runs axially backward as far as the rear end of the barrel. The extension passes through an end wall at the rear end of the barrel and the extension and the end wall are mutually sealing.
In accordance with another aspect of the present invention, the first and second line segments have a connected state where the first line segment is connected to a rear end of the second line segment and a disconnected state where the first line segment is disconnected from the rear end of the second line segment. In the connected state, the first line segment defines a limit for a rearward displacement of the second line segment, and in the disconnected, the second line segment is displaceable rearwardly beyond the limit.
The present invention also provides a spray gun for coating objects with a coating material, the gun comprising a grip, a barrel, a coating-material feeding duct and a plug member. The grip has therein a first longitudinal channel. The barrel has opposite front and rear end openings and a second longitudinal channel extending through an entire length of the barrel from the front end opening to the rear end opening. The barrel is connected to the grip so that the first and second channels are communicated with each other. The coating-material feeding duct runs through the first and second channels. The plug member has opposite front and rear portions and an intermediate portion connecting the front and rear portions. The front and intermediate portions are sized and shaped to be receivable within the second channel and removable from the second channel via the rear end opening of the barrel. The rear end portion is sized and shaped to close the rear end opening in a sealing manner. The front portion of the plug member is made hollow and defines a segment of the coating-material feeding duct.
Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description thereof are to be regarded as illustrative in nature, and not as restrictive.
This problem is solved by the invention by the features of claim 1.